This invention relates to a system for analyzing matter adhered to the inside wall of a vessel. Diseases such as arteriosclerosis occurs due to adhesion of matter, such as cholesterol ester, fatty acid and protein, to the inside wall of a vessel. A medical treatment for such diseases is different depending on what is the adhered matter. So, only if it can be found easily what is the matter adhered to the inside wall of a vessel, it will be of great help to the treatment of such diseases.